I use several credit cards for day-to-day purchases-- purely for ease of financial management and record keeping. I pay all balances off each month-- so never get hit with the usurious interest banks charge folks who carry a balance.
This month, I used my Discover card for a big purchase and the statement total was $841 and change. But here's the kicker-- the minimum payment was $7.88. That's less than one percent of the amount owed!!
If you're impulsive, lack self-control, max-out your credit cards and carry a balance-- unless your name is Methuselah, you'll never even come close to breaking even. You will have paid more than your lifetime net worth in interest...